The present invention relates to a manual adjustment device for regulating the stroke length of a non-rotatable rod-shaped adjustment member that can be axially displaced between two limit positions by means of a switchable stepping motor and by way of a motion conversion mechanism. More particularly, the invention relates to a manual adjustment device for use in a vehicle if there is a malfunction in the electronic system of the vehicle.
In the construction of engines and vehicles, electronically controlled stepping motors are employed which regulate movement between two limit positions by means of a motion conversion mechanism. For example, German Patent 3,901,722 (corresponding to U.S. Pat. No. 5,080,063) discloses a mechanical speed regulator that is equipped with an electronically controlled adjustment device for fuel injection pumps in internal combustion engines, wherein a stepping motor is provided to correct the quantity of fuel in the range between full load and starting revolutions and a control device that processes engine and ambient parameters is provided for actuation of the stepping motor. If the electronic system malfunctions, it is no longer possible to make an adjustment if, for example, the limit position for the starting revolutions has been attained, so that the loaded motor vehicle can no longer be driven to the nearest service station.